This invention relates generally to a calibration system and method therefor and, more importantly, to a calibration system and method for work machines using electro hydraulic controls.
Many work machines use electro hydraulics to control a wide variety of different work elements connected thereto. The precise control of such work elements is useful not only with respect to the accuracy and degree of efficiency in accomplishing the particular work application, but also when the functioning of the implement is automatically controlled. Unfortunately, the various components used to control such work elements are subject to wear and tear over time, thereby reducing their accuracy. This is exacerbated by the rugged conditions under which work machines are typically used. In addition, since several components are typically used in combination to control any given work element, their tolerances tend to xe2x80x9cstack upxe2x80x9d, thereby decreasing an operator""s ability to accurately control the work element. This lack of control also causes unnecessary wear and tear on the work element itself, thereby reducing its effectiveness, further shortening the work element""s life span, and increasing the overall costs for maintaining the work machine.
In some cases, the control accuracy of the implement or work element can be improved by using low tolerance components. However, such components are expensive. Moreover, they too are subject to wear and tear and, as a result, cannot provide a long-term solution. The accuracy of the control of the work element can also be improved by simply replacing components whose tolerances exceed a proper level. However, such a replacement strategy is very expensive and results in a lot of wasted components. Moreover, it requires continuous monitoring of the components and work elements to determine when they should be replaced, and given such human intervention, it increases the risk that a component or work element is not replaced when necessary.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.
A calibration system for a work machine using an electro hydraulic valve to control the operation of a work element via a hydraulic circuit which includes various detectors, such as sensors positioned in communication with components of the work machine for detecting the state of the components and an actuator coupled to the work element for controlling the operation thereof is disclosed.
In one aspect of the present invention, the calibration system comprises use of a service tool such as a laptop computer adapted to generate a calibration initialization signal and further comprises a controller positioned in communication with the service tool and the various relevant sensors, the controller being operable to receive the calibration initialization signal from the service tool and output appropriate signals to the relevant components. In this regard, the controller includes a command signal generator for generating a command signal having a command value for transmission to the relevant component upon receipt of the calibration initialization signal. The detector detects when the component has reached the command state and generates a detector signal having a value representing a calibration factor to be used in correlating the detector signal value with the actual state of the component.
In another aspect of the present invention, the controller is adapted to automatically and dynamically calibrate various components of the work machine without input from a service tool. With respect to the operator input device which is adapted to move through a plurality of travel angles from a neutral position to a corresponding plurality of operator input device positions for controlling movement of the work element and which outputs an operator input device signal having an operator input device signal value indicative of the position of the operator input device, the controller includes a storage mechanism for storing the plurality of travel angles of the operator input device. The controller also includes a correlation mechanism in communication with the operator input device which is adapted to receive the operator input device signal for correlating the received signal with a travel angle of the operator input device. The comparator is in communication with the correlation mechanism and the storage mechanism and continuously compares the correlated travel angle at each limit position of the operator input device with the corresponding last stored travel angle for that particular limit position. The detector of the controller is in communication with the comparator and detects differences between the compared correlated travel angle and the compared last stored travel angle, the controller storing the compared correlated travel angle within the storage mechanism such that accurate control of the operator input device is achieved.
In yet another embodiment of the automatic calibration embodiment of the present invention, an actuator mechanism position sensor is positioned in communication with the actuator mechanism for sensing a position of the actuator mechanism, and outputs an actuator mechanism position sensor signal having an actuator mechanism position sensor signal value indicative of the travel distance of the actuator mechanism. The controller is in communication with the actuator mechanism position sensor and is likewise adapted to automatically and dynamically calibrate the actuator mechanism position sensor. Specifically, the storage mechanism of the controller stores a plurality of travel distances for the corresponding limit positions of the actuator mechanism. The correlation mechanism, which is in communication with the actuator mechanism position sensor and receives the actuator mechanism position sensor signal, correlates the actuator mechanism position sensor signal with a travel distance of the actuator mechanism. The comparator, which is in communication with the correlation means and the storage means, compares the correlated travel distance associated with each limit position of the actuator mechanism with the corresponding last stored travel distance for that particular limit position, while the detector detects differences between the compared correlated travel distance and the compared last stored travel distance. The controller stores the compared correlated travel distance within the storage mechanism of the controller such that accurate control of the actuator mechanism is also achieved.
In yet a further embodiment of the automatic calibration embodiment of the present invention, wherein the work machine includes a pressure sensor positioned in communication with the control valve for sensing a pressure being exerted against the actuating cylinder and outputting a pressure sensor signal having a pressure sensor signal value indicative of the sensed pressure, the controller, which is in communication with the pressure sensor, automatically and dynamically calibrates the pressure sensor signal value to the value of the atmospheric pressure when the hydraulic system pressures are discharged and are at or near atmospheric pressure. In particular, the storage mechanism stores a predetermined atmospheric pressure; the comparator, which is in communication with the pressure sensor, compares the stored atmospheric pressure to the pressure sensor signal value of the received pressure sensor signal when the system is at or near atmospheric pressure; the detector detects differences between the stored atmospheric pressure and the compared pressure sensor signal value when the system is at or near atmospheric pressure; and the calculator calculates an atmospheric pressure calibration factor representing the detected difference such that accurate control of the pressure sensor is achieved.
In another aspect of the present invention, the controller is adapted to automatically and dynamically calibrate various components of the work machine without input from a service tool. With respect to the operator input device which is adapted to move through a plurality of travel angles from a neutral position to a corresponding plurality of operator input device positions for controlling movement of the work element and which outputs an operator input device signal having an operator input device signal value indicative of the position of the operator input device, the controller includes a storage mechanism for storing the plurality of travel angles of the operator input device. The controller also includes a correlation mechanism in communication with the operator input device which is adapted to receive the operator input device signal for correlating the received signal with a travel angle of the operator input device. The comparator is in communication with the correlation mechanism and the storage mechanism and continuously compares the correlated travel angle at each limit position of the operator input device with the corresponding last stored travel angle for that particular limit position. The controller stores the compared correlated travel angle within the storage mechanism.
In yet another embodiment of the automatic calibration embodiment of the present invention, an actuator mechanism position sensor is positioned in communication with the actuator mechanism for sensing a position of the actuator mechanism, and outputs an actuator mechanism position sensor signal having an actuator mechanism position sensor signal value indicative of the travel distance of the actuator mechanism. The controller is in communication with the actuator mechanism position sensor and is likewise adapted to automatically and dynamically calibrate the actuator mechanism position sensor. Specifically, the storage mechanism of the controller stores a plurality of travel distances for the corresponding limit positions of the actuator mechanism. The correlation mechanism, which is in communication with the actuator mechanism position sensor and receives the actuator mechanism position sensor signal, correlates the actuator mechanism position sensor signal with a travel distance of the actuator mechanism. The comparator, which is in communication with the correlation means and the storage means, compares the correlated travel distance associated with each limit position of the actuator mechanism with the corresponding last stored travel distance for that particular limit position. The controller stores the compared correlated travel distance within the storage mechanism of the controller such that accurate control of the actuator mechanism is also achieved.
In yet a further embodiment of the automatic calibration embodiment of the present invention, wherein the work machine includes a pressure sensor positioned in communication with the control valve for sensing a pressure being exerted against the actuating cylinder and outputting a pressure sensor signal having a pressure sensor signal value indicative of the sensed pressure, the controller, which is in communication with the pressure sensor, automatically and dynamically calibrates the pressure sensor signal value to the value of the atmospheric pressure when the hydraulic system pressures are discharged and are at or near atmospheric pressure. In particular, the storage mechanism stores a predetermined atmospheric pressure; the comparator, which is in communication with the pressure sensor, compares the stored atmospheric pressure to the pressure sensor signal value of the received pressure sensor signal when the system is at or near atmospheric pressure; the calculator calculates an atmospheric pressure calibration factor.